Physics at the Large Hadron Collider (LHC) and the International e + e − Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined.4

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Production of the Standard Model Higgs-boson at the photon collider at TESLA is studied for Higgs-boson masses above 150 GeV. A simulation of signal and background processes takes into account realistic luminosity spectra and detector effects. In the considered mass range, large interference effects are expected in the W + W − decay channel. By reconstructing W + W − and ZZ final states, not only the h → γγ partial width can be measured, but also the phase of the scattering amplitude. This opens a new window onto the precise determination of the Higgs-boson couplings. Models with heavy, fourth-generation fermions and with enlarged Higgs sector (2HDM (II)) are considered.

The ratio of the CKM quark-mixing matrix elements |V ub |/|V cb | has been measured using B hadron semileptonic decays. The analysis uses the reconstructed mass M X of the secondary hadronic system produced in association with an identified lepton. Since B → X u ℓν transitions are characterised by hadronic masses below those of the D mesons produced in B → X c ℓν transitions, events with a reconstructed value of M X significantly below the D mass are selected. Further signal enrichments are obtained using the topology of reconstructed decays and hadron identification. A fit to the numbers of decays in the b → u enriched and depleted samples with M X above and below 1.6 GeV/c 2 and to the shapes of the lepton energy distribution in the B rest frame gives |V ub |/|V cb | = 0.103 +0.011 −0.012 (stat.) ± 0.016 (syst.) ± 0.010 (model) and, correspondingly, a charmless semileptonic B decay branching fraction of BR(B → X u ℓν) = (1.57 ± 0.35 (stat.) ± 0.48 (syst.) ± 0.27 (model)) × 10 −3 .